Numerous observational studies and case reports have suggested a potential link between COVID-19 and the prolongation of the QT interval on ECG4,8,13-15,20-22,35,36. To address the limitations of confounding factors and reverse causality inherent in observational research27, we conducted an MR analysis to investigate whether COVID-19 has a genetic causal impact on QT interval changes. In summary, our findings did not support a causal effect of COVID-19 on longer or shorter QT intervals. These conclusions are derived from large GWAS sample datasets, multiple robust MR assessments, and confirmatory analyses. Nevertheless, considering the differences between our MR results and observational findings, we contemplate two possible explanations. These disparities may, in part, stem from the limitations of observational studies, including challenges related to confounding factors and reverse causality. Additionally, measurements of the QT interval on ECG may be influenced by various factors, including medication usage and individual physiological conditions.
In addition to specific single-gene inherited mutations that cause congenital long QT syndromes, acquired factors affecting QT interval duration are complex37,38. The QT interval reflects the contribution of multiple ion currents, including potassium and calcium ion channels, to the cardiac action potentials. Ion channels are essential for various cellular functions and have been implicated as key host factors in many viral infections4,14. A recently published GWAS analysis of genetic variants in patients with severe COVID-19 identified 49 genomic loci associated with disease susceptibility or severity, implicating processes including inflammatory signaling, immune metabolism, and blood coagulation25. These findings provide novel insights into COVID-19-mediated multisystem complications. However, the complex biological pathways underlying COVID-19-induced arrhythmias, specifically QT interval prolongation, remain poorly understood. Emerging evidence suggests that SARS-CoV-2 genes encode K+ channels and may interfere with the regulation of Ca2+ handling in cardiomyocytes, leading to impaired cardiac contractility and increased risk of arrhythmias15. An MR analysis supports the indication of a causal effect between serum calcium levels and QT interval prolongation from the UKB39, whereas it is not known whether the relationship between COVID-19 and QT interval is mediated through changes in serum calcium concentration or other potential mediators affected by COVID-19. Our evidence suggests that COVID-19 does not directly influence QT interval changes, and, based on current understanding, much work remains to decipher which biomolecules or indicators play a mediating role in their correlation.
During a pandemic, multiple factors such as myocarditis, electrolyte disturbances, hormonal changes, and autonomic nervous system dysfunction can influence QT interval4,7,40,41. Mechanistically, excessive inflammation may alter the expression and function of several ion channels, especially K+ and Ca2+ channels, resulting in inflammatory cardiac channelopathies, QT prolongation, and arrhythmias11,42. Therefore, SARS-CoV-2 infection is associated with myocarditis and alterations in internal physiological factors7. Our MR analysis employing genetic variants of COVID-19 as the IVs may not fully account for these complex processes. Additionally, the multifaceted nature of COVID-19-induced inflammatory responses and multi-organ complications poses challenges for elucidating the pathogenic mechanisms of potential complications, including QT interval prolongation1,5,11. Furthermore, the association between COVID-19 and QT interval prolongation may involve undiscovered genetic or environmental factors. Notably, certain existing drugs, such as chloroquine and lopinavir, have been widely discussed for their potential to cause QT prolongation when used in COVID-19 treatment43-50. These drugs, however, had previously been reported to cause QT prolongation by targeting the KV11.1 potassium channel even before the emergence of COVID-19 and untreated COVID-19 patients also exhibited QT interval prolongation4,14,43,51. The MR analysis results are independent of the genetic variants influenced by drug effects in COVID-19. Further research on the causal relationship between specific medications and QT interval prolongation can help explain how drugs may affect QT intervals during COVID-19 treatment.
Consideration of the temporal relationship between exposure and outcome is of paramount importance. COVID-19 is a complex and dynamic disease, and the timing of ECG measurements concerning the infection process may hold significant implications12. The impact of COVID-19 on QT intervals might vary with different stages of the disease, and our MR analysis did not adequately capture this temporal factor. To comprehensively understand the intricate relationship between COVID-19 and QT intervals, more datasets covering diverse population cohorts and different disease stages will provide deeper insights into the underlying genetic factors and potential mechanisms governing the association.
Furthermore, although our study did not find a genetic causal relationship between COVID-19 and QT interval prolongation, it does not rule out the possibility that COVID-19 infection may increase the risk of QT interval prolongation or arrhythmias. GWAS summary statistics for COVID-19 and QT interval duration are continually evolving to identify novel variants. For example, in the GWAS summary of QT intervals we included, despite meticulous consideration of polygenic risk-equivalent variants and single-gene putatively pathogenic rare variants, over 75% of individuals with markedly prolonged QT (>480 ms) did not exhibit these genetic variants29. This suggests that our understanding of the genetic factors influencing QT duration is limited and underscores the substantial influence of non-genetic factors on QT intervals.
To the best of our knowledge, this study represents the inaugural application of MR to scrutinize the causal association between COVID-19 and the QT interval. The research utilized the most extensive available genome-wide association data for exposure and outcome, employing both fundamental and advanced MR methods for effect estimation. Multiple sensitivity analysis approaches were employed to confirm the robustness of the findings, furnishing largely unbiased causal estimates. Nevertheless, the study is not without limitations. One notable constraint is the absence of data from non-European populations, thereby constraining the generalizability of the conclusions. Moreover, the possibility that unmeasured variables, impacting both COVID-19 and the QT interval, remains unaccounted for, necessitating further exploration to enhance our understanding of the underlying mechanistic relationships. Hence, it is essential to acknowledge that our findings warrant replication and validation in alternative datasets and diverse populations. In summary, forthcoming investigations should capitalize on larger, more diverse, and comprehensive datasets to account for increased variance, enabling a more robust genetic inference of the link between COVID-19 infection and QT intervals. Such endeavors will offer supplementary evidence for the prevention and management of cardiac complications associated with COVID-19.